Apparatus for setting the air gap between an inductor and a valve seat

ABSTRACT

A device and method for setting the air gap between a valve seat and an inductor which is movable with respect thereto comprising a circuit including, in series, the inductor, the valve seat and an electrical indicating means for making an indication only when the inductor and seat are in electrical contact to complete the series circuit and means for using this circuit to set the aforementioned air gap.

United States Patent Bryant Feb. 13, 1973 54 APPARATUS FOR SETTING THE AIR 3,441,701 4/1969 Seuleu et al. ..219 10.43 GAP BETWEEN AN INDUCTOR AND A 2,551,757 5 1951 Mittlemann ..219 10.77

[75] Inventor:

US. Cl. ..2l9/l0.77, 219/1041, 266/5 E Int. Cl. ..H05b 5/04 Field of Search..2l9/l0.77, 10.75, 10.41, 10.43,

References Cited UNITED STATES PATENTS 2,757,268 7/1956 Edwards ..219/l0.75

DETECTOR Primary ExaminerR. F. Staubly Assistant ExaminerB. A. Reynolds Attorney-James H. Tilberry et a1.

[57] ABSTRACT A device and method for setting the air gap between a valve seat and an inductor which is movable with respect thereto comprising a circuit including, in series, the inductor, the valve seat and an electrical in- 15 Claims, 4 Drawing Figures 52 g 54 82 B 2F Q? 42% i X% E 40 Q i a: i $5 a: i 24 Q 26 20 B C 10 X 30 22 363,2

APPARATUS FOR SETTING THE AIR GAP BETWEEN AN INDUCTOR AND A VALVE SEAT This invention pertains to the art of induction heating and more particularly to a method and apparatus for setting the air gap between an inductor and a valve seat in an induction heating installation for heating the valve seat.

The invention is particularly applicable for use in inductively heating the valve seats of an internal combustion engine, and it will be described with particular reference thereto; however, it must be appreciated that the invention has much broader applications and may be used in various apparatus for inductively heating valve seats and similar conical or cylindrical surfaces.

With the advent of low lead gasoline, it has become necessary to harden the exhaust valve seats of an internal combustion engine to increase their wear characteristics. In accordance with one apparatus for accomplishing this heating operation, a series of inductors are supported on a movable platen in spaced relationship to the exhaust valve seats. Each of these inductors is secured onto an element slidably received within the platen in a manner to be biased away from the platen and toward the individual valve seats. During the operation of this apparatus, the platen is moved forward so that the inductors themselves engage the individual valve seats. In this manner, the inductors are properly positioned with respect to the valve seats, irrespective of variations in the mutual relationships between the valve seats. When all inductors are contacting their respective valve seats, the elements carrying the inductors are locked with respect to the platen.

The platen is then moved away from the valve seats a distance corresponding to the desired air gap needed between the inductors and the valve seats for proper induction heating. This draws all inductors from the valve seats this selected distance to establish the same air gap at each inductor. After this movement, the inductors are energized and the valve seats are inductively heated for subsequent quench hardening by air or liquid. This type of apparatus has proven extremely satisfactory in hardening the individual exhaust port valve seats of an internal combustion engine and is described in more detail in copending application Ser. No. 151,493, filed June 9, 1971. In the arrangement described above and disclosed in the above-identified application, one of the most important control aspects is the proper positioning of the individual inductors with respect to the valve seats just prior to energizing the inductors for the heating operation. If the spacing between one inductor and its valve seat is not within prescribed limits, the exhaust port may not be properly heated. This will require rejection and reheating.

To assure that the proper spacing is realized between each inductor and its valve seat, it has been suggested to apply a known power source across each inductor and to measure, with a digital volt meter, the voltage across each inductor before the heating operation is started. By knowing the proper voltage which is realized with a desired air gap between the inductor and valve seat, this measured voltage is indicative of the proper spacing between the inductors and the valve seats. The voltage across each of the inductors is measured after the inductors are drawn back from the valve seats by retraction of the platen. It has been found that this type of measuring arrangement is generally useful;

however, it does not provide a positive approach to maintain accurate spacing of the individual inductors. This is primarily due to the fact that variations in the spacing of an inductor from the valve seat does not have a drastic effect upon the voltage across the inductor. Consequently, by measuring the voltage across the inductor, a truly accurate indication of proper spacing is not as positive as desired. In some cases, the inductor may be in contact with the valve seat without developing a measurement indication of this fact.

In accordance with the present invention, there is provided a method and apparatus for detecting physical contact between the inductors and their valve seats and for using this detected contact to obtain a more positive control over the spacing between the inductors and the valve seats. In addition, this detector method and apparatus can indicate when there is a malfunction in the device mechanism for moving the several inductors toward the valve seats and in the mechanism for clamping the inductors to the platen preparatory to moving the inductors from the valve seats to establish the proper air gap for induction heating.

In accordance with the present invention, there is provided a device for detecting physical contact between a valve seat and an inductor movable with respect thereto which device comprises a circuit including, in series, the inductor, the valve seat and an electrical indicating means for making an indication only when the inductor and valve seat are in electrical contact and the circuit is electrically completed. By using this device with respect to each of the several inductors in the device for hardening valve seats, physical contact between each inductor and its valve seat can be determined both when the inductor is to be in engagement with the valve seat and when the inductor is to be spaced from the valve seat. In this manner, the inductors all start from a valve seat engagement position. If the clamping device operates, then there is positive control over the air gap because all of the inductors are moved in unison by the platen to which the several inductors are locked. This gives a positive control over setting the air gaps of the inductors. If one of the clamping devices should malfunction, the inductor will remain in contact with the valve seat as the other inductors are moved away from their valve seats. This condition is also detected by the above defined contact detecting device. In this manner, the most critical defect of having the inductor in engagement with the valve seats during the actual heating operation is avoided.

In accordance with another aspect of the present invention there is provided a method of inductively heating two, adjacent, generally conical valve seats with two spaced inductors having shapes generally matching the valve seats, the method comprises the steps of mounting the inductors on a movable element or platen for movement of the inductors with respect to the platen and along generally parallel axes generally coaxial with the valve seats, biasing the inductors in a direction along the axes and away from the platen, moving the platen toward the valve seats in a direction generally parallel to the axes and into a first position where the inductors contact the valve seats and are forced toward the movable platen against the bias, detecting an electrical contact between the valve seats and the inductors, locking the inductors with respect to the platen in response to a detected electrical contact between each of the inductors and its respective valve seat, shifting the platen away from the valve seats in a direction generally parallel to the axes and a predetermined distance generally corresponding to a desired coupling gap between each of the inductors and its valve seat, and energizing the inductors to inductively heat the respective valve seats. By following this method, the proper air gap is obtained between the inductors and the valve seats. This method is further expanded to provide additional detecting steps after the platen is shifted away from the valve seats and before the inductors are energized. This method provides an indication of whether or not the clamping arrangement of the method has been performed and all of the inductors have been moved away from their respective valve seats.

The primary object of the present invention is the provision of an apparatus and method for detecting physical contact between a valve seat and an inductor used to heat the valve seat and using this physical contact detection for setting the desired air gap, which apparatus and method employs a series circuit including the inductor and the valve seat and electrical means responsive to'completion of this circuit by physical contact between the valve seat and the inductor.

Another object of the present invention is the provision of an apparatus and method for detecting physical contact between a valve seat and an inductor used to heat the valve seat and using this physical contact detection for setting the desired air gap, which apparatus and method is positive in operation and easily incorporated into existing equipment for inductively heating valve seats by inductors movable with respect thereto. Still another object of the present invention is the provision of an apparatus and method for detecting physical contact between a valve seat and an inductor used to heat the valve seat, which apparatus and method can be used to assure that the inductor is properly spaced from the valve seat to create a desired air gap preparatory to induction heating.

Another object of the present invention is the provision of an apparatus and method for detecting physical contact between a valve seat and an inductor used to heat the valve seat and using the contact detection for setting the desired air gap, which apparatus and method employs a transformer with a first winding in a circuit comprising a valve seat and the inductor, in series, and a second winding for controlling an indicating mechanism upon contact of the inductor with the valve seat.

These and other objects and advantages will become apparent from the following description used in conjunction with the accompanying drawings in which:

FIG. I is a side elevational view showing, schematically, the apparatus in which the present invention is used and certain aspects of the present invention;

FIG. 2 is an enlarged cross-sectional view taken generally along line 22 of FIG. 1;

FIG. 3 is a schematic wiring diagram showing one embodiment of the electrical aspects of the present invention used in the apparatus of FIG. 1; and,

* FIG. 4 is a schematic wiring diagram illustrating a preferred embodiment of the wiring diagram employed in the present invention.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting same, FIG. 1 shows a device A for inductively heating two adjacent, conical valve seats B, C located within the exhaust ports 10, 12 of an engine head 14. In accordance with the invention, a number of valve seats are simultaneously heated; however, for the purpose of illustrating the present invention, only two adjacent valve seats are illustrated. Induction heating device A is basically the same as illustrated in prior patent application Ser. No. 151,493 filed June 9, 1971, and that disclosure is incorporated by reference herein. In that prior application, a plurality of adjacent valve seats are inductively heated by an apparatus which is schematically illustrated in FIG. 1 and which includes inductors 20, 22 for each of the valve seats B, C, respectively. These inductors are secured onto support heads 24, 26 having outwardly extending guides 30, 32 for registration with bores 34, 36, respectively. In this manner, the inductors are centered with respect to the valve seats, since the bores and valve seats are concentric. Support heads 24, 26 are, in turn, supported on movable rods 40, 42, respectively. These rods reciprocate within a movable platen 50 and include rearward stops 52, 54 on one side of the platen and. biasing springs 56, 58 on the otherside of the platen. By this structure, the inductors 20, 22 are biased away from the platen 50 and toward the respective valve seats. Each of the inductors is energized by an appropriate power supply, schematically represented as sources 60, 62. In accordance with the present invention, there is incorporated into circuitry for each of the inductors a detector 70, 72. These detectors form an essential part of the present invention and will be described in detail following a general description of the operating characteristics of apparatus A.

Platen 50 is movable in guides 80, 82 in a direction indicated by the arrow, which direction is parallel to the central axes x, y of inductors 20, 22. Various arrangements could be used for moving platen 50; however, in accordance with the illustrated embodiment of the present invention, a rack 84 secured onto the platen is driven by a rotatable pinion 86 which is connected, in turn, to a motor 90 by link 92. An appropriate control device 94 drives the pinion 86 in the proper direction anclthrough the proper angle to cause movement of platen 50 in a manner to be described later. Associated with each of the rods 40, 42 there is a locking, or clamping, device 100, 102, respectively. Since these devices are substantially identical, only device need be explained in detail, and this explanatio'n will apply equally to the locking or clamping device 102.

Referring now to FIG. 2, the locking, or clamping, device 100 includes a cylinder for driving a rod 112 in a direction indicated by the arrow. Rod 112 includes a stop 114 and a seal 116. Surrounding rod 40 there is provided a clamp ring 1 18 having outwardly extending terminal ends 118a, l18b. In operation of the clamping device 100, movement of rod 112 upwardly releases stop 114 from end 118a. The resiliency of clamp ring 118 then causes end 118a to move away from end 1l8b. In this manner, the ring is resiliently expanded to release the rod 40. In this condition, the rod 40 is freely movable with respect to the platen.

Cylinder 110 then moves rod 112 downwardly engaging end 118a with stop 114 and moving the ends together. This clamps the ring 118 around rod 40 to lock the rod onto platen 50. The purpose of this clamping function is clearly described in the prior patent application and will be hereinafter described in relation to its use with the present invention.

To heat inductively valve seats B and C, platen 50 is moved by pinion 86 into position E shown in FIG. 1, from the position F at the upper end of the distance designated b. In position E, inductors 20, 22 physically contact the valve seats B, C. Rods 40, 42 are not clamped to the platen; therefore, the rods may move backwardly against the biases of springs 56, 58 as platen 50 is moved forward to bring the inductors into actual physical contact with the valve seats. By using the biasing springs, contact by both inductors is generally assured, irrespective of slight axial offset of the spaced inductor or of the valve seats themselves. To heat inductively it is generally required that the inductor be spaced a selected distance from the workpiece being heated, which spacing is referred to as the air gaplln accordance with the preferred embodiment of the present invention, the desired air gap between inductors 20, 22 and valve seats B, C is approximately .046 inches. To set the air gap of each inductor, the rods 40, 42 are locked or clamped onto the platen 50 by actuation of cylinders 110. Thereafter, pinion 86 moves the platen 50 away from the valve seats a distance a which is the desired air gap. When this movement has been completed, power supply sources 60, 62 are energized to heat the valve seats inductively. Thereafter normal air quenching quench hardens the valve seats to provide a case hardened surface thereon. After this operation takes place, platen 50 is moved backwardly to the distance designated b to position F.

This removes the inductors and guides 30, 32 from the exhaust ports 10, l2'so that the engine head 14 can be removed and a subsequent engine head can be positioned under the inductors. When this occurs, the cylinders 110 again release the rods 40, 42 and the rods move forward until stops 52, 54 engage the platen 50 by the action of springs 56, 58. The apparatus A is in condition for repeating the process described above.

To assure proper operation of the apparatus A, the inductors 20, 22 must be in physical contact with the valve seats when the platen has been moved forward. If there is not physical contact, then the desired air gap will not be realized when the platen is moved backwardly a distance a. Also, if one of the clamps should inadvertently fail, there will'be physical contact between the inductor and the valve seat after the platen has been moved back the distance a. From this analysis of the above defined apparatus, it is seen that optimum operation of the apparatus can be monitored by determining whether or not the inductors are in physical contact with the valve seat when the platen is moved forward and when the platen is moved backwardly the distance a into the heating position. The present invention is directed toward detectors 70, 72 for detecting physical contact and controlling the apparatus A in accordance with the existence of physical contact when vtheplaten is moved forward and the non-existence of physical contact when the platen is moved backwardly.

Referring now to FIG. 3, there is schematically illustrated a wiring diagram for practicing the present invention. ln accordance with this diagram, transformers 200, 202 include primary windings 210, 212 and secondary windings 214, 216. The secondary winding of each transformer is connected to one of the inductors 20, 22 so that the winding, inductor, and valve seat are in a se ries circuit which circuit is completed when the inductor contacts the valve seat, as indicated by the dashed lines 220, 222. A 12 volt power supply 230 energizes the primary windings 210, 212 to actuate indicating means, shown in this embodiment as relay coils 232, 234, which, in turn, control a circuit 240 that uses the detection of physical contact to control the operation of apparatus A. Circuit 240 may take a variety of forms in adapting the detector means to the operation of apparatus A.

Referring first to the operation of the detectors 70, 72, when the power supply 230 is energized, power is applied to the primary windings 210, 212. if the inductors are not grounded by physically contacting the valve seats, the secondary windings 214, 216 reflect or induce a substantially high impedance across the primary windings 210, 212. A low current flow, thus, occurs in the primary winding and this current is not sufficient to actuate the contacts associated with relay coils 232, 234. If the inductor 20 contacts valve seat B, the series circuit is completed between the inductor and the valve seat. This, substantially reduces the impedance of the series circuit and causes a reduction in the impedance experienced by primary winding 210. When this occurs, current flow through the primary is increased to actuate the contacts associated with relay coil 232. The same action takes place when the power supply 230 is actuated and the inductor 22 is in physical contact with valve seat C. In summary, if either of the inductors is grounded to the valve seat, the relay coil in the particular detector device associated with the grounded inductor is actuated to indicate such physical contact. This indication can be a simple light or other visual indicator; however, in accordance with the illustrated embodiment of the invention the indicator device is incorporated into the operating functions of apparatus A for heating spaced valve seats.

Referring now to circuit 240, relay coil 232,when subjected to sufficient current caused by grounding of inductor 20, operates normally closed contact 332a and normally opened contact 332b, 3320 and 332d. in a like manner, coil 234 actuates normally closed contact 234a and normally opened contacts 234b, 234c and 234d. These contacts perform indicating and control functions for apparatus A. Contacts 232b'and 234b actuate circuits including indicator lights 240, 242. Consequently, when the power supply 230 is energized and one of the inductors is grounded, the light associated with that inductor is on. This gives a visual indication of physical contact between a particular inductor and'its valve seat. Contact 2320 is in a circuit including a clamp control 244 associated with clamping device 100. When this contact is closed, indicating that there is physical contact between the inductor 20 and valve seat B, clamping device may be actuated. Clamp control 246 is operated in a like manner when normally opened contact 2340 is closed. Consequently, when both inductors are grounded and the platen is moved forward, the indicator lights 240, 242 are turned on and the clamping control devices 244, 246 are energized to allow clamping of the rods 40, 42, with respect to the platen for subsequent retraction or back-off of the platen 50 the distance shown in FIG. 1.

vWhen contacts 232d, 234d are both closed, this indicates that there is physical contact between inductors 20, 22 and their respective valve seats B, C. This energizes retract control 250 so that platen 50 can be moved backwardly the distance a corresponding to the desired air gap between the inductors and their valve seats. Before retraction of platen 50, the power supply 230 is disconnected and the various contacts associated with coils 232, 234 are shifted to their. normal conditions. This can be done by de-energizing power supply 230 and allowing normal spring returns to reset the contacts.

After retraction, it is again desirable to detect any physical contact between the inductors and the valve seats to determine if, inadvertently, one of the clamps failed or something else occurred to prevent retraction of one or both of the inductors from its valve seat. To accomplish this subsequent detection, retract control 270 is actuated to again connect the 12 volt power supply 230 across the circuit including the primary windings 210, 212. In this stage of the operation of apparatus A, there should be no physical contact between the inductors and the valve seats. If either of the inductors is still in physical contact with its valve seat, one of the indicator lights 240, 242 will be lighted. In addition, one of the contacts 232a or 234a will be opened. Opening of one of these contacts precludes operation of the heating cycle for apparatus A and indicates a malfunction in the desired retraction of one of the inductors. Various arrangements could be used for precluding energization of the power sources 60, 62 when physical contact is indicated after the retract operation. Circuit 240 includes off controls 272, 274 which are actuated when current is flowing in the lines 280, 282. When both of these two controls 272, 274 is actuated, the power supply 60, 62 can energize the inductors. If one of these controls is not actuated, it indicates physical contact of the associated inductor and heating is precluded. When contact 232a is open indicating physical contact between inductor and valve seat B, off control 272 is not actuated. In a like manner, when contact 234a is open because of physical contact between inductor 22 and valve seat C, off control 274 is not actuated. When either of these off controls are not actuated, power cannot be directed to the inductor.

Control 276 is the device for energizing the power supply 230 when the platen is first moved forward to contact the valve seats by the inductors. The control 270 and the control 276 are selectively energized so that the detector devices 70, 72 are energized when I physical contact between the inductors and valve seats is to be tested. These two positions, in apparatus A are first when the platen is moved forward to bring the inductors in contact with the valve seats, and second when the platen is retracted the distance a to set the air gaps. In the first position, physical contact by all inductors is necessary to establish the proper air gap. In the second position, physical contact is an indication of a malfunction and should preclude heating of the valve seats by the inductors.

Referring now to FIG. 4, there is illustrated a more detailed wiring diagram for incorporating the present invention into the apparatus A for inductively heating valve seats. In accordance with this embodiment, transformers 300, 302 include primary windings 310, 312 and secondary windings 314, 316. Power lines 320, 322 are connected across a plurality of parallel electrical branches which will be described later. Relays 330, 332 correspond with relays 232, 234 of FIG. 3 and form elements for detecting physical contact between the inductors 20, 22 and the respective valve seats B, C. They are operated in accordance with the previous description of the physical contact detecting devices 70, 72. Relay 330 controls normally open contacts 330a, 33% and normally closed contact 3300. In a like manner, relay 332 controls normally open contacts 332a, 332b and normally closed contact 3320. Referring now to branch 340, this branch includes the normally closed contact 330c, normally closed contact 332c and a relay 342 which, in turn, controls normally open contacts 342a, 342b. This branch is used primarily to indicate physical contact between an inductor and its valve seat when one of the contacts 330c, 332c is opened.

Parallel branch 350 is a light indicator branch and is actuated when normally open contact 330b is closed to energizing indicator light 352. Similarly, parallel branch 354 includes an indicator light 356 which is energized when normally open contact 332b is closed. Electrical branch 360, which is the cycle start branch, includes a cycle starting switch 362, a platen advance control 364, a relay 366 controlling normally open contacts 366a, 366b, and a normally closed contact 368a controlled by relay 368. After the platen has been advanced, the branch 370 is closed by a limit switch 372 operated by forward movement of the platen to the position E shown in FIG. 1. This energizes relay 374 controlling a normally open contact 374a. This in turn energizes detector devices 70, 72 and branch 380 appearing at the top of FIG. 4. This branch also includes previously mentioned normally open contact 374a and a normally closed contact 382a controlled by relay 382 which also controls normally open contacts 382b, 382a.

Referring now to parallel branch 390, which is the clamping and back-off branch, this branch includes previously mentioned normally open contacts 342a, 382b for energizing the clamping device 392 and the back-off device 394 which backs the platen 50 away from the valve seats the distance a to establish the desired air gap. When platen 50 is moved away from the forward position into the heating position, limit switch 372 is again opened which de-energizes relay 374 and disconnects detector devices 70, 72 by opening normally open contact 374a in branch 380. The rearward movement of platen 50 then actuates branch 400 including a limit switch 402 which is closed when the platen is retracted the distance of the desired air gap. This energizes a relay 404 having normally open contacts 404a, 404b to again apply voltage across the detectors70, 72 by closing the contact 404a. Contact 366b having been previously closed by the cycle start button 362.

The above description basically outlines the general components of the circuit shown in FIG. 4 and certain essential operating characteristics. The general operation of this circuit is quite apparent from the above energized. During forward movement of the platen the inductors 20, 22 should be in physical contact with the valve seats B, C. if this occurs, increased current flow through relays 330, 332 energizes these relays which opens contacts 3300, 332c to de-energize relay 342. This opens contact 342a in branch 390 and contact 342b in the heating branch. The heating branch includes a heat control 410 for controlling heating sources 60, 62 and heat start switch 412. This branch cannot be energized because contacts 342a and 404b are open. Relays 330, 332, when actuated, also close contacts 330a, 332a which actuates relay 382. This opens contact 382a which deenergizes detector devices 70, 72 which actuates relay 342 and closes contacts 342a, 342b. Also, relay 382 closes contact 382b in branch 390 which establishes this branch causing clamping device 392 to actuate the clamping devices 100, 102. This clamps the rods 40, 42 with respect to the platen 50. Thereafter, back-off device 394 draws the platen 50 back a distance corresponding to the desired air gap. This closes limit switch 402 in branch '400 to energize relay 404. This relay closes contact 404a in branch 380 to again reactivate detectors 70,72 since contact 366b remains closed. In this position, there should be no physical contact between the inductors and the respective valve seats. Consequently, the operation will be described in accordance with the operation wherein no physical contact is realized. in this case, the impedance of primary windings 310, 312 are high because the circuit including the inductors and valve seats are open. Consequently, relays 330, 332 are not energized. Branch 340 remains closed to energize relay 342. This closes relay 342b in the heating branch of the circuit. Since limit switch 402 is now closed, contact 404b' in the heating circuit is also closed. Con sequently, heating can now take place by actuating switch or other control 412. When this is done, inductors 20, 22 are energized by power sources 60, 62 for the desired time to heat inductively the respective valve seats B, C. At the same time, switch or control 412 is energized, relay 368 is also energized. This opens contact 368a and de-energizes relay 366. This opens contact 366b in branch 380 to disconnect the detector devices 70, 72 prior to the heating cycle. Also, when relay 366 is de-energized, contact 366a is de-energized in the circuit including relay 382 the function of which will be described in connection with a situation where physical contact exists when the platen is moved to the air gap position. Opening of contact 366a resets the branch including relay 382 for subsequent operation.

Referring now to the situation where platen 50 is moved into the air gap position and physical contact exists between one or both of the inductors and their respective valve seats, it will be assumed that inductor 20 is in contact with valve seat B. This is not desired and heating should not occur. To prevent heating, relay 330 is energized. This opens contact 330c and, thus, deenergizes relay 342. This opens contact 342b in the heating branch of the circuit and heating cannot be effected. At the same time, contact 330b is closed. This lights indicator light 350 indicating that the inductor 20 is in contact with its valve seat. This is a malfunction and appropriate attention is given'to the apparatus A to correct this difficulty.

Referring now to the branch including relay 382, this branch is connected across the power lines 320, 322 when platen is moved forward into the forwardmost position. If both inductors 20, 22 are in contact with their valve seats', which is the desired function, contacts 330a, 332a are closed. This actuates relay 382 closing contact 382a which holds the circuit energized. At the same time, contact 382a is open to disconnect the detectors 70, 72 prior to movement of platen 50 in a backward direction. This prevents arcing when the inductor is moved from its contact with the valve seat. Energization of the relay 382 also closes contact 382b which coacts with contact 342a in branch 390 to actuate the clamping arrangement as previously described. If by chance there is no physical contact between one of the inductors and its valve seats after the platen is moved into the forward direction E, neither relay 342 nor relay 382 will be energized. Consequently, the detector means 70, 72 will remain energized, one of the lights 352 or 356 will be off and no clamping and backoff can occur by action of branch 390. This will stop the further operation of apparatus A and clearly indicates that one or both of the inductors are not seated. The relays 342, 382 assure that no heating takes place if one or more of the inductors are in contact with the valve seats when the platen is in the air gap position.-

Limit switch 372 is open when platen 50 is started to be moved backwardly into the air gap position. This deenergizes relay 374 and opens contact 374a in branch 380. This also assures disconnection of the detector devices 70, 72 during the retract or back-off operation of platen 50.

After the heating operation, the platen is moved rearwardly to allow removal of the workpiece including the valve seats. This opens limit switch 402 which deenergizes relay 404. This in turn opens contact 404a disconnecting the detector devices. In a like manner,

contact 404b is open to assure no heating takes place.

This is a general description of the operation of ap' paratus A incorporating the invention of the present application. Of course, various circuitry changes are well within the ordinary skill of the art and could be made without departing from the intended scope and spirit of the present invention.

I claim:

1. In a device for inductively heating a generally conical valve seat, including a generally circular inductor having a circumference generally matching said seat, means for moving said inductor into contact with said seat, means for retracting said inductor from said seat a distance corresponding to a known air gap between said inductor and said seat and means for energizing said inductor to heat inductively said valve seat, the improvement comprising: detector means for determining when said inductor is in contact with said valve seat, said detector means including a transformer having inductively coupled first and second windings, a first circuit including said first winding, means for applying a voltage across said first winding, a means actuatable in response to a given electrical condition of said first winding, a second circuit including said second winding and said inductor with said second winding having a first grounded end and a second end electrically connected to said inductor whereby said second end is grounded when said inductor contacts said valve seat, and said first winding having said given electrical condition when said second end of said second winding is grounded.

2. The improvement as defined in claim 1 wherein said first winding has a first impedance when said second end is grounded and a second impedance when said second end is electrically disconnected from said valve seat and, said given electrical condition is said second impedance.

3. The improvement as defined in claim 1 wherein said actuatable means is a relay having an operating coil in electrical series with said first winding.

4. The improvement as defined in claim 1 including means for selectively actuating said voltage applying means.

5. The improvement as defined in claim 4 wherein said actuating means includes means for actuating said voltage applying means after said inductor moving means has been actuated and before said inductor retracting means has been actuated.

6. The improvement as defined in claim 5 wherein said actuating means includes means for actuating said voltage applying means after said inductor retracting means has been actuated.

7. The improvement as defined in claim 4 wherein said actuating means includes means for actuating said voltage applying means after said inductor retracting means has been actuated.

8. In a device for inductively heating two adjacent,

generally conical valve seats, said device including first and second generally circular inductors each having a circumference generally matching one of said valve seats, means for moving said inductors, in unison, toward and away from said valve seats, means for allowing movement of said inductors with respect to said moving means, means biasing said inductors from said moving means toward said valve seats, means for locking said inductor with respect to said moving means, means for shifting said moving means toward said valve seats into a first position with said inductors contacting said valve seats, means for then actuating said locking means, and means for then shifting said moving means away from said valve seats into a second position having a distance from the first position generally corresponding to a desired air gap between said inductors and said valve seats for inductive heating thereof, the improvement comprising separate electrical means for detecting physical contact of each of said inductors with its respective valve seat when said moving means is in said first position.

9. The improvement as defined in claim 8 including means for indicating said physical contact of said inductors and valve seats.

10. The improvement as defined in claim 8 wherein each pfsaid contact detecting means comprises a series circuit including a detector, one of said inductors and one of said valve seats which circuit is completed upon contact of said inductor and seat.

11. The improvement as defined in claim 10 wherein said detector of said series circuit is a first winding inductively coupled with a second winding, means for applying a voltage across said second winding and means responsive to a change in current in said second winding.

12. The improvement as defined in claim 8 wherein said contact detecting means includes means for also detecting physical contact between said inductors and said valve seats when said moving means is in said second position.

13. The improvement as defined in claim 12 including means for preventing energization of said inductors when said detecting means detect physical contact between a valve seat and an inductor.

14. A method of inductively heating two adjacent, generally conical valve seats with two spaced inductors having shapes generally matching said valve seats, said method comprising the steps of:

a. mounting said inductors on a movable element for movement of said inductors with respect to said element and along generally parallel axes generally coaxial of said valve seats;

. biasing said inductors in a direction along said axes and away from said element;

. moving said element toward said valve seats in a direction generally parallel to said axes and into a first position where said inductors contact the valve seats and are forced toward said element against said bias;

. detecting an electrical contact between said valve seats and said inductors;

e. locking said inductors with respect to said elements in response to a detected electrical contact between each of said inductors and its respective valve seat;

f. shifting said element away from said valve seats in a direction generally parallel to said axes and a predetermined distance generally corresponding to a desired coupling gap between each of said inductors and its valve seat; and,

g. energizing said inductors.

15. The method as defined in claim 14 including the step of again detecting an electrical contact between said valve seats and said inductors after said shifting step and before said energizing step.

* i h t 

1. In a device for inductively heating a generally conical valve seat, including a generally circular inductor having a circumference generally matching said seat, means for moving said inductor into contact with said seat, means for retracting said inductor from said seat a distance corresponding to a known air gap between said inductor and said seat and means for energizing said inductor to heat inductively said valve seat, the improvement comprising: detector means for determining when said inDuctor is in contact with said valve seat, said detector means including a transformer having inductively coupled first and second windings, a first circuit including said first winding, means for applying a voltage across said first winding, a means actuatable in response to a given electrical condition of said first winding, a second circuit including said second winding and said inductor with said second winding having a first grounded end and a second end electrically connected to said inductor whereby said second end is grounded when said inductor contacts said valve seat, and said first winding having said given electrical condition when said second end of said second winding is grounded.
 1. In a device for inductively heating a generally conical valve seat, including a generally circular inductor having a circumference generally matching said seat, means for moving said inductor into contact with said seat, means for retracting said inductor from said seat a distance corresponding to a known air gap between said inductor and said seat and means for energizing said inductor to heat inductively said valve seat, the improvement comprising: detector means for determining when said inDuctor is in contact with said valve seat, said detector means including a transformer having inductively coupled first and second windings, a first circuit including said first winding, means for applying a voltage across said first winding, a means actuatable in response to a given electrical condition of said first winding, a second circuit including said second winding and said inductor with said second winding having a first grounded end and a second end electrically connected to said inductor whereby said second end is grounded when said inductor contacts said valve seat, and said first winding having said given electrical condition when said second end of said second winding is grounded.
 2. The improvement as defined in claim 1 wherein said first winding has a first impedance when said second end is grounded and a second impedence when said second end is electrically disconnected from said valve seat and, said given electrical condition is said second impedance.
 3. The improvement as defined in claim 1 wherein said actuatable means is a relay having an operating coil in electrical series with said first winding.
 4. The improvement as defined in claim 1 including means for selectively actuating said voltage applying means.
 5. The improvement as defined in claim 4 wherein said actuating means includes means for actuating said voltage applying means after said inductor moving means has been actuated and before said inductor retracting means has been actuated.
 6. The improvement as defined in claim 5 wherein said actuating means includes means for actuating said voltage applying means after said inductor retracting means has been actuated.
 7. The improvement as defined in claim 4 wherein said actuating means includes means for actuating said voltage applying means after said inductor retracting means has been actuated.
 8. In a device for inductively heating two adjacent, generally conical valve seats, said device including first and second generally circular inductors each having a circumference generally matching one of said valve seats, means for moving said inductors, in unison, toward and away from said valve seats, means for allowing movement of said inductors with respect to said moving means, means biasing said inductors from said moving means toward said valve seats, means for locking said inductor with respect to said moving means, means for shifting said moving means toward said valve seats into a first position with said inductors contacting said valve seats, means for then actuating said locking means, and means for then shifting said moving means away from said valve seats into a second position having a distance from the first position generally corresponding to a desired air gap between said inductors and said valve seats for inductive heating thereof, the improvement comprising separate electrical means for detecting physical contact of each of said inductors with its respective valve seat when said moving means is in said first position.
 9. The improvement as defined in claim 8 including means for indicating said physical contact of said inductors and valve seats.
 10. The improvement as defined in claim 8 wherein each of said contact detecting means comprises a series circuit including a detector, one of said inductors and one of said valve seats which circuit is completed upon contact of said inductor and seat.
 11. The improvement as defined in claim 10 wherein said detector of said series circuit is a first winding inductively coupled with a second winding, means for applying a voltage across said second winding and means responsive to a change in current in said second winding.
 12. The improvement as defined in claim 8 wherein said contact detecting means includes means for also detecting physical contact between said inductors and said valve seats when said moving means is in said second position.
 13. The improvement as defined in claim 12 including means for preventing energization of said inductors when said detecting meAns detect physical contact between a valve seat and an inductor.
 14. A method of inductively heating two adjacent, generally conical valve seats with two spaced inductors having shapes generally matching said valve seats, said method comprising the steps of: a. mounting said inductors on a movable element for movement of said inductors with respect to said element and along generally parallel axes generally coaxial of said valve seats; b. biasing said inductors in a direction along said axes and away from said element; c. moving said element toward said valve seats in a direction generally parallel to said axes and into a first position where said inductors contact the valve seats and are forced toward said element against said bias; d. detecting an electrical contact between said valve seats and said inductors; e. locking said inductors with respect to said elements in response to a detected electrical contact between each of said inductors and its respective valve seat; f. shifting said element away from said valve seats in a direction generally parallel to said axes and a predetermined distance generally corresponding to a desired coupling gap between each of said inductors and its valve seat; and, g. energizing said inductors. 